Power circuits in a System 3-7 game

Every game has +5 VDC regulated logic, +12 VDC unregulated (Williams calls it unregulated 5 V), +100 and -100 VDC for the displays, +28 VDC for coils and flippers, +18 VDC for the lamp matrix and 6.3 VAC GI. Hot Tip and Lucky Seven add 300 VDC, System 7 adds -12 VDC, and Firepower II and later add 50 VDC for the flippers.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• No +5 V on a System 3-6 power supply
• No +5 V on a System 7 power supply
• Early Black Knights use the System 6 power supply
• What the power supply board takes in and puts out
• Test the power supply with its outputs unplugged
• Spare diodes, capacitors and resistors for System 3-7
• Swapping power supply boards between generations
• High-voltage supply rebuild parts, System 3 to 11C

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part One, Clay Harrell (pinrepair.com)